Cerebral aerography.

Abstract

Throughout the present decade and the one immediately preceding it, cerebral aerography has been used extensively in centers where neurosurgery is well established. The creation of unnatural density differences within the cranial vault, produced by the removal of cerebrospinal fluid and the introduction of air or some other gas, has proved itself to be an uncommonly effective means of providing detailed information concerning intracranial lesions prior to surgical attack. Either of two means of replacing fluid with air can be used to advantage in the study of intracranial situations. The two procedures, air encephalography and ventriculography, have individual spheres of utility and are not to be considered as competing technics. Air encephalography, accomplished by puncture of the cisterna magna through the foramen magnum or by lumbar puncture, allows for the indiscriminate removal of fluid from the subarachnoid spaces and the ventricular system alike providing that the normally communicating formula are not obstructed. As the result, when the withdrawn fluid is replaced with gas, the greatly increased transparency of the normally fluid-filled spaces provides an opportunity to observe the inner as well as the outer surfaces of the brain. Actually air encephalography finds its greatest use when surface lesions are anticipated. Brain atrophy can be identified by the appearance of greatly deepened cortical sulci and correspondingly widened subarachnoid spaces (Fig. 1), and adhesive arachnoiditis results in the complete obliteration of subarachnoid spaces over the surface of the brain in the area involved. Meticulous technic in the matter of fluid withdrawal and the delivery of gas into the subarachnoid space, as well as in the preparation of roentgenograms of high quality, is essential if pneumoencephalography is to yield its best results. Ventriculography calls for direct ventricular tap through a surgical opening in the skull, drainage of cerebrospinal fluid from the ventricular system, replacement of fluid with gas, and the preparation of many accurately executed stereoscopic pairs of roentgenograms. This procedure is not one which is to be undertaken lightly. As its descriptive name implies, it provides, when successfully carried out, an opportunity to examine all or a part of the ventricular system of the brain in its true relationship to recognizable bony landmarks. Alterations from the expected size, shape, and position of the various cavities within the brain can often be translated into terms which describe the location, the extent, and sometimes the character of the lesion under consideration. It is axiomatic that ventriculography is reserved for use in situations where symptoms and signs indicate beyond reasonable doubt that some serious intracranial abnormality exists. When clinical signs of increased intracranial pressure are encountered, ventriculography is the only aerographic technic which is permissible.